Podcast: Wine Physics

Richard Feynman once commented that “if you look at a glass of wine closely enough, you will see the entire universe.” On today’s podcast, we take a little wine tour of our own, to explore some of the physics behind the reds, whites, and rosés. First, we catch up with Martino Reclari, an expert on oenodynamics: the physics of wine swirling. Reclari and his collaborators developed a mathematical treatment of the standing wave patterns formed in a glass as it’s shaken. The three dimensionless parameters they derived can be applied to any container size, from the glass in your hand to the thousand-liter bioreactors mixing nutrients to cultivate cells. The work was nominated for an Ig Nobel Prize in 2012, but Reclari isn’t shaken. “In a sense, it’s a bit scary being nominated for that. It means your research is a little weird and not very useful,” he says, “but in fact…the research nominated is usually research that increases understanding of the normal people of the physics, so why not?”

Close-up view of a refractometer used to measure the sugar content in grapes.
Image Credit: Meg Rosenburg

The second stop on our physics-of-wine tour takes us out into the field with Matthew Rawn, co-owner of Two-Mountain Winery in Washington’s Yakima Valley. Rawn describes how a hand held instrument called a refractometer helps winemakers make harvest decisions by measuring the sugar contents of the grapes on the vine. Light passing through a sample of grape juice is bent, or refracted, by different amounts depending on the exact proportion of sugar and water in the juice. The refractometer measures that angle of refraction and compares it to the Brix scale, which lets winemakers decide when to bring in the harvest, depending on the varieties of wine they want to make.

On our final stop, we chat with Dan Quinn, a postdoctoral research fellow at Stanford University, who made a popular YouTube video explaining why “legs” or “tears” of wine form on the side of your glass. The key to the process lies in the difference in surface tension between alcohol and water. When alcohol in the thin film of wine on the glass evaporates, it raises the surface tension of the remaining solution enough to continue drawing wine up the side of the glass. Droplets form and slide down under gravity over and over again. Quinn’s novel approach to the topic – recording the phenomenon and speeding up the footage – reveals how dynamic the process is, and with more than 130,000 views, the video has a wide reach. “If you’re not inspired or excited,” he contends, “then you’re not going to look for the papers, look in the textbooks, not going to want to learn more, so you’ve got to start somewhere. I think that’s why science videos are really important in the grand scheme of science.”

Thus concludes our science-soaked wine tour. Cheers!

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